1. Field of the Invention
The present invention relates in general to water heater performance monitoring and, more particularly, to a system and method for using water heating rates to determine whether a water heater is functioning optimally.
2. Description of Related Art
Gas water heaters are typically constructed with a burner to heat water stored in a water tank. The burner is typically located directly below the water tank, and transfers heat to the water in the water tank via conduction through the water tank bottom. Problems with a water heater can impede this transfer of heat to the water in various ways (e.g., sediment buildup inside the water tank, defects in the manufacture of the water heater, misassembly of the water heater, damage to the water heater), thus slowing down the rate at which the water is heated. Such a reduction in the rate of heat transfer can undesirably affect the efficiency of the water heater, resulting in higher fuel usage and decreased water heating capability.
To address the problem of reduced heat transfer rates between the burner and the water in the water tank of a water heater, detection and warning systems have been used. For instance, in U.S. Pat. No. 6,265,699 B1 (the '699 patent), an electronic control for an electric water heater measures heating rates of water near electric heating elements of the water heater and, when the heating rate falls below a threshold level, sends an error indication to a user. Such an approach, however, can falsely identify or fail to identify problems with the operation of the water heater. By way of example, the control described in the '699 patent would send an error indication to a user after a single heating cycle having a heating rate below a threshold level. The fact that the device in the '699 patent relies on a single heating cycle to determine whether the water heater is functioning properly would likely result in a substantial number of false alarms due to normal fluctuations in heating rate from one heating cycle to the next.
Additionally, the '699 patent uses a preprogrammed threshold heating rate to determine whether the water heater is functioning properly. Such a preprogrammed threshold heating rate does not account for variations in heating rates between different water heaters, nor does it account for variations in the different environments in which water heaters may be installed. Consequently, it would be desirable to have a gas water heater performance monitoring system and method that filters out the effects of at least some external and/or short-term factors in determining when to alert a user that the water heater requires service.